Structure and Properties of Thermomechanically Processed Chitosan-Based Biomimetic Composite Materials: Effect of Chitosan Molecular Weight

While natural biopolymers are promising sustainable resources to develop “green” materials, their unique properties make it challenging to process them as synthetic polymers, limiting their applications. This is mainly due to the intramolecular and intermolecular hydrogen bonds formed by the large number of −OH and other polar groups in natural biopolymers. Thermomechanical processing allows the breakage of the intramolecular and intermolecular hydrogen bonds and thus increases chain mobility. In this work, biomimetic materials based on chitosan and silk peptides were prepared by thermomechanical processing. The effect of different molecular weights of chitosan on the structure and properties of the composites was investigated. A combination of excellent strength (σ_t = 29.8 MPa) and toughness (ϵ_b = 100.5%) was obtained with a certain molecular weight of chitosan, and the toughness (ϵ_b = 143.4%) could be further enhanced by rehydration after drying. Consequently, this research demonstrated that the molecular weight of chitosan significantly influences the structure and properties of the composites. The results of the study provide a reference for the processing of natural polymeric materials by hot-melt methods.